Peroxidases (E.C. 1.11.1.7) are enzymes that catalyze the oxidation of a substrate (an electron or hydrogen donor) with hydrogen peroxide. Such enzymes are known from microbial, plant and animal origins, e.g. peroxidase from Coprinus cinereus (cf. e.g. EP 179,486). They are typically hemoproteins, i.e. they contain a heme as a prosthetic group.
It has been found that peroxidases, utilizing hydrogen peroxide as substrate, are able to enhance the bleaching effect of hydrogen peroxide during washing. The use of peroxidases for bleaching stains on fabrics is described in WO 89/09813. It has also been found that coloured substances leached from dyed fabrics could be bleached by means of peroxidases together with hydrogen peroxide. The use of peroxidases for inhibiting dye transfer in this way is described in WO 91/05839.
Certain oxidizable substrates, e.g. metal ions and phenolic compounds such as 7-hydroxycoumarin (7HCm), vanillin (VAN), and p-hydroxybenzenesulfonate (pHBS), have been described as accelerators or enhancers, able to enhance bleaching reactions (cf. e.g. WO 92/18683, WO 92/18687, and Kato M and Shimizu S, Plant Cell Physiol. 1985 26 (7), pp. 1291-1301 (cf. Table 1 in particular). In WO 94/12621 other types of enhancing agents are disclosed, e.g. phenothiazines and phenoxazines.
It is the object of this invention to provide a peroxidase with improved bleaching performance at high pH.